This is a Model U-238 (cute name) GM detector
produced by the Goldak Company of Glendale California. In the late 1940s,
Goldak specialized in the manufacture of equipment designed to locate
underground objects such as cables and pipes (the company is still in
business). According to Curt Cassingham, his father Larry Cassingham
worked for Goldak at that time and suggested that they expand their line
of products to include radiation detectors. Apparently, Goldak wasn't
interested so Cassingham left the company and started up Detectron. The
only other radiation detector manufactured by Goldak that I know of is the
Model 200 ( the Colorado) and I
have not managed to locate any references to the Model U-238. It looks
like it was manufactured in the late 1940s or early 1950s. Perhaps Goldak
saw that Detectron was doing well in the nuclear business, and the U-238
was a half-hearted attempt to compete. It was likely designed for use by
uranium prospectors. The detector window, twelve small plastic covered
holes in the case (six on the side and six on the bottom), is very similar
to that of Detectron's
DG-5 detector.